In a content distributing business for distributing a content via a communication network, services that target music and video are already widely spread, but in recent years, an attention on a service targeting an electronic book is enhanced. Also, when entries of existing publishers and the like increase and a large number of quality electronic books are provided together with printed products or as substitutes for printed products, and electronic book market is expected to swiftly expand.
A dedicated-use terminal apparatus for viewing an electronic book or electronic book viewing software (hereinafter, which may be referred to as “electronic book viewer”.) is currently available. A user of a terminal apparatus having a communication function installed with the electronic book viewer, which is, for example, a personal computer (PC), a mobile phone device, or a smart phone, can download an electronic book from a so-called electronic book site and enjoy it by the electronic book viewer.
Electronic books that can be downloaded from the electronic book site include computerized print media such as books including a comic and a novel and a photo collection. It should be noted that the electronic books in the present specification are not limited to these and include computerized print media such as a news paper, a magazine, a product catalog, and a free newspaper which are provided from a newspaper company and a publisher.
Incidentally, in a general mode for the content sharing service in conventional various Web services, a user decides whether to belong to a specific field (for example, a network space) or a sharing group or not. The user participating the sharing group passively accepts a situation where an existing user in the field or the group (another member previously belonging to the group) improves and expands the content with regard to the content already shared by him/herself. Also, the user belonging to the sharing group defers expansion and limitation of a sharing range to another group member by way of participation of a new member and withdrawal of an existing member.
On the other hand, a technique of sharing a content with another user in the same space on a network space where users gather is proposed (Patent Literature 1).